The automatic calibration of hydraulic model aims to improve the accuracy of the model of water supply network intelligent management. Currently, the genetic algorithm is widely used for automatic of hydraulic model. In view of problems that the standard genetic algorithm has slow convergence and can be easily trapped in local optimal, the paper makes some improvements of this algorithm. Simulated annealing algorithm is used to stretch the fitness function and the roulette wheel selection method combining elitism strategy is replacing the traditional selection method. Besides, the similarity function is added to avoid the breeding with closest relatives in cross operator and the double convergence criteria is used to reduce unnecessary computation time. The improved genetic algorithm is used to calibrate the water supply hydraulic model of G. The results show that the improved genetic algorithm has better efficiency and accuracy.